1. Field of the Invention
The present invention relates to a brake master cylinder assembly for automotive vehicles, and more particularly to a brake master cylinder assembly including a pressure chamber for generating high braking pressure during actual braking and an annular pressure chamber for supplying low pressure fluid into the pressure chamber for braking during idle.
2. Description of the Prior Art
In the conventional brake master cylinder assembly, a stepped piston operatively connected to a brake pedal or brake booster is disposed in a stepped axial bore of a cylinder body defining a pressure chamber in communication through an outlet with the vehicle brakes. The pressure chamber generates high braking pressure for braking the vehicle while in motion, that is, the actual braking stage. The brake master cylinder also includes an annular pressure chamber for supplying low pressure fluid into the pressure chamber for braking the vehicle while at idle. In known brake master cylinders, the pressure in the annular chamber is limited, by a relief valve, to a maximum which is below a predetermined pressure to eliminate clearance between the brake pads or brake shoe and disc or drum, respectively.
In the conventional brake master cylinder assembly, however, the pressure in the annular chamber is generated by the force transmitted directly from the brake pedal or the brake booster thereby requiring increased brake pedal depressing force when the car is at idle.
The present invention is intended to provide a brake master assembly wherein the force required for depressing the brake pedal is reduced from that required by conventional brake master assemblies. Furthermore, the present invention provides a brake master cylinder assembly wherein the volume of low pressure fluid supplied from the annular pressure chamber into the pressure chamber communicating with the brakes may be constant.